Magneto inductive flow measuring systems with pole shoes are known in the state of the art. These provide volumetric flow measurement in a measuring tube using electrodynamic induction. Present are measuring electrodes, which ascertain a measurement voltage. This is induced by producing a magnetic field directed perpendicularly to entrained, charge carriers of a medium flowing through the measuring tube and arranging the measuring electrodes essentially perpendicularly to the flow direction of the medium and perpendicularly to the direction of the magnetic field. The measurement voltage induced in the measuring electrodes is proportional to the flow velocity of the medium averaged over the cross section of the measuring tube and, thus, proportional to the volume flow rate. In the case of known density of the medium, the mass flow of the medium in the measuring tube can also be determined. For tapping the measurement voltage, most often two measuring electrodes are provided, thus a measuring electrode pair. The pair of electrodes is located bracketing the measuring tube axis where magnetic field strength is maximum, thus in the region of the expected maximum measurement voltage.
For example, published international application, WO 2008/028872 A1 discloses a magneto inductive flow measuring device for measuring volume flow or mass flow of a medium in a pipeline and comprises a measuring tube, through which the medium flows in the direction of the measuring tube axis, a magnet system, which produces a magnetic field passing through the measuring tube and extending essentially transversely to the measuring tube axis, coupled with the medium at least one measuring electrode, which is arranged in a region of the measuring tube lying essentially perpendicular to the magnetic field, and a control/evaluation unit, which, based on the measurement voltage induced in the at least one measuring electrode, delivers information concerning the volume flow or mass flow of the medium in the measuring tube.
Known from published international application, WO 2011/091899 A1 is another magneto inductive flow measuring device. In this case, a first coil component with a coil body for accommodating a pole core of a coil is provided, wherein the coil on the coil body and the coil core are arranged in a first opening of the coil body with a longitudinal axis of the coil core being coaxial to the coil. The coil core includes a molding and the coil body a stop, which is arranged between measuring tube and coil. The coil core is formed as a pole shoe. Arranged between coil core and measuring tube is at least one pole sheet, wherein each pole sheet is separately snapped in the mounted state of the same into a depression provided in the coil body. The coil body includes at least one cable guide for guiding a cable, so that the guided cable of a predetermined length does not exceed a certain separation from the coil body.
During the positioning of a cable, especially a coaxial cable, in a magneto inductive flow measuring system in the region of the pole shoe and/or coil core, there is the danger that the cable becomes pinched or damaged by metal edges located there. Damage to the cable to the coil core can lead to short circuiting, especially in the presence of vibrations during operation the magneto inductive flow measuring system.